Bag for sterilisation

ABSTRACT

The invention relates to a packaging bag for the sterilisation of food, comprising walls on which a closing device is arranged comprising complementary closing profiles, said bag being characterised in that: 
     the material constituting the walls has a softening point above 100° C., and 
     the complementary closing profiles are adapted to hermetically seal the bag when it is placed in an atmosphere of temperature above 80° C. 
     The invention also relates to a method of sterilising food products by use of such a bag.

FIELD OF THE INVENTION AND PRIOR ART

The present invention relates to the field of packaging bags, in particular packaging bags made of thermoplastic materials.

The invention also relates to the field of the sterilisation and the preservation of foods.

The sterilisation and the preservation of foods is a technique well known in itself, and practised for many years by private individuals and by professionals.

Preserves are traditionally produced in glass pots or jars, which are resistant to high temperature and make it possible to protect their contents hermetically from the exterior environment.

Few innovations have been proposed to date to renew this practice of preservation of foods. However, glass jars have certain drawbacks: in particular, they are heavy, fragile and bulky. As a result, they moreover require particular precautions by the users thereof, as well as by the producers thereof.

Bags have moreover been proposed, such as for example in the document U.S. 20060285778, which describes a flexible bag re-closable by means of closing profiles, and, the internal walls of which are covered, below said profiles and at the level of the lateral ends of the bag, with a material adapted to locally seal the walls of the bag when heat is applied.

The bag described in this document is thus not suited to the sterilisation of food, since it cannot be hermetically sealed.

The document DE19951050 describes a bag provided with closing profiles, the profiles of which are covered with an adhesive layer to increase their adherence and simplify their shape.

Such a bag is not suited to the sterilisation of food, since the adhesive layer does not enable a hermetic seal.

The document WO91/01927 describes a method of industrial sterilisation of food in dedicated bags, sealed beforehand with the exception of an opening for escaping steam, which closes during sterilisation.

DESCRIPTION OF THE INVENTION

The aim of the present invention is thus to renew this offer with regard to the sterilisation and preservation of foods, while overcoming the aforementioned drawbacks of the prior art.

In this respect, the invention proposes a packaging bag for the sterilisation of food, comprising walls on which a closing device is arranged comprising complementary closing profiles, said bag being characterised in that:

-   -   the constituent material of the walls has, at a temperature of         100° C., sufficient resistance to retain its confinement         properties, and     -   the complementary closing profiles are adapted to hermetically         seal the bag when it is placed in an atmosphere of temperature         above 80° C.

Advantageously, but optionally, the packaging bag according to the invention moreover comprises at least one of the following characteristics:

-   -   The walls of the bag are made of a material forming oxygen         barrier.     -   The walls of the bag are made of a material from the following         group: polypropylene, polyethylene terephthalate polypropylene         complex, or polypropylene-polyamide complex.     -   The walls of the bag have a melting temperature above 120°.     -   The bag comprises several pairs of complementary closing         profiles, arranged at different distances from the mouth of the         bag.     -   At least one pair of complementary closing profiles has several         locking levels.     -   At least one pair of complementary closing profiles is at least         partially covered with an adhesive activatable from a         temperature of 50° C., said bag being hermetically sealed by         melting of the adhesive when it is placed in an atmosphere of         temperature above 50° C.     -   At least one female profile has a cavity shaped engaging part,         in which is arranged a strip of adhesive activatable from a         temperature of 50° C.     -   At least one pair of complementary closing profiles has engaging         parts having a melting temperature comprised between 60° C. and         80° C., the bag being hermetically sealed by melting of the         engaging parts when it is placed in an atmosphere of temperature         above or equal to the melting temperature of the engaging parts.     -   The engaging parts are composed of a polymer of ethylene vinyl         acetate or ethylene ethyl acrylate, coextruded on the walls of         the bag.     -   The complementary closing profiles are profiles of revolving         cylinder section.     -   The closing device is positioned near to the mouth of the bag         formed by the upper edges of the walls, but set back with         respect to said upper edges of the walls of the bag.

The invention moreover relates to the use of a packaging bag according to the invention for the sterilisation and the preservation of food products.

To this end, the invention proposes a method of sterilising food products, comprising the steps consisting in:

-   -   inserting, into a bag according to the invention, a quantity of         food products to be sterilised,     -   closing the bag by means of the closing device of the bag,     -   heating the bag, filled and closed in an atmosphere, to a         temperature above or equal to 100° C.,     -   maintaining the bag at temperature until the closing device         hermetically seals the bag and until the food products are         sterilised.

DESCRIPTION OF DRAWINGS

Other characteristics, aims and advantages of the present invention will become clearer on reading the description that follows, and by referring to the appended figures, given by way of non-limiting examples and in which:

FIG. 1 represents a packaging bag, seen in perspective, according to the invention.

FIGS. 2 a to 2 e illustrate different embodiments of closing devices used in the packaging bag according to the invention.

FIG. 3 shows an embodiment wherein the closing device has several locking stages.

FIG. 4 shows an embodiment wherein the closing device comprises several pairs of profiles, at least one adapted to make it possible to seal the bag.

FIGS. 5 a to 5 c illustrate steps of a method of sterilisation during which the packaging bag according to the invention is used.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIG. 1, a packaging bag 1 according to the invention is represented. Said bag preferably comprises two walls 10 and 11, delimited by edges, respectively upper 12 and lower 13, and transversal 19 edges.

The walls 10, 11 of the bag may be the subject of numerous embodiments. They may preferably be walls made of thermoplastic materials.

These walls 10 and 11 may be mono or multilayer and mono or multi material. Typically, they may be made from a plastic film, or from a sheet of complex material such as a paper support covered with a layer of thermoplastic material or instead a thermoplastic metallised layer.

However, they are preferably made of a material capable of withstanding a temperature above 100° C., in other words made of a material having a sufficient resistance, at least at a temperature of 100° C., to retain its mechanical and chemical properties of confinement of food products. For example, the Vicat softening point of the material is strictly above 100° C. Typically such a material may be an oxygen barrier material such as polypropylene (PP) or polyethylene terephthalate (PET) or another oxygen barrier material such as a polypropylene/polyamide complex or a PET-PP complex, said materials having a melting temperature above 100° C.

Said two walls 10 and 11 may be obtained from a single and same film turned back along the lower edge 13, and welded along the two transversal parallel edges 19.

In a variant, said two walls 10 and 11 may be constituted of two separate sheets, in other words two distinct entities, assembled on three of their sides.

The upper edges 12 of the walls 10 and 11 form a mouth E of the bag 1.

The bag 1 is moreover provided with a closing device 20, arranged on the walls 10 and 11, advantageously towards the inside of the bag. Moreover, the closing device 20 is preferably positioned near to the mouth E of the bag 1. However, it is advantageously positioned with a slight set back with respect to the upper edge 12 of the walls 10 and 11 of the bag 1, in order that the bag can be opened and closed by taking hold of it by a part of the walls 10 and 11 positioned between the closing device 20 and the edge 12 of the walls.

According to the invention, the bag is adapted to withstand at least a temperature of 100° C., and preferably a temperature above 120° C., which is ensured by the material constituting the walls, for example polypropylene (PP) or polyethylene terephthalate (PET), which has a melting temperature strictly above 100° C., typically 120° C.

Moreover, according to the invention, the closing device 20 is adapted to hermetically seal the bag 1 when it is placed in an atmosphere at a temperature above 80° C., typically at a temperature of 100° C.

To do this, several embodiments may be envisaged, certain of which are represented in FIGS. 2 a to 2 e.

Said closing device 20 may be constituted of separate elements of the walls 10 and 11, transferred thereon for example by welding, or formed integrally with them, for example coextruded with the walls.

The closing device 20 may be constituted of complementary profiles 21, 22, such as male 21 and female 22 profiles.

Moreover, to enable the bag 1 to be sealed, the closing profiles 21, 22, may be constituted, at least in part, of a solid material adapted to attain a sufficient level of softening to enable the welding of the two profiles 21, 22, at a temperature of the order of 100° C.

For example, the parts 212 and 222 of the profiles and 22 forming the engagement and enabling the closing of the bag may be constituted of a polymer of ethylene vinyl acetate (EVA) or ethylene ethyl acrylate (EEA), the melting temperature of which is comprised between 60° C. and 80° C. This embodiment is illustrated in FIGS. 2 a and 2 c.

The parts 211 and 221 of the profiles 21 and 22 linked to the walls 10 and 11 may then be made of the same material as these (typically PP).

Alternatively, the engaging parts 212 and 222 of the profiles 21 and 22 may be covered, partially or totally, by a heat activatable adhesive (thermoactivatable), in other words activatable at a temperature above 50° C., typically at a temperature of the order of 100° C. This is represented in FIGS. 2 b and 2 d. Thus, by placing the bag 1 in an atmosphere at a temperature of 100° C., the adhesive is activated by the temperature and joins together the engaging parts 212 and 222, to hermetically seal the bag 1.

Finally, and with reference to FIG. 2 e, an alternative embodiment is represented wherein an engaging part 222 of a female profile 22, in the form of a cavity, is partially filled with a strip of thermoactivatable adhesive, in other words heat activatable, typically at a temperature above 50° C., and preferably at a temperature of the order of 100° C.

In FIG. 2 e may be observed a particular embodiment wherein the male profile 21 has, on the engaging part 212 thereof, a point shape of triangular section, and the engaging part 222 of the female profile 22 is a complementary shape thereof. Then the strip of adhesive C arranged in the cavity 222 formed by the female profile may take a revolving cylinder section shape.

According to an alternative embodiment, the closing device 20 of the bag 1 may comprise two complementary profiles, at least one of which comprises more than one locking stage.

A particular example of such a closing device is represented in FIG. 3, wherein the closing comprises a male profile 21 and a female profile 22, the male profile being provided with a stem 213 equipped with two levels of protrusions 214, and the female profile 22 comprising two levels of ribs 223 adapted to cooperate with the protrusions 214 of the male profile. The female profile 22, respectively the male profile 21, may thus have one level of ribs or more, respectively one level of protrusions or more, which enables numerous embodiments to be envisaged.

Reference may also be made to the patent application n°FR1156444 for other embodiments.

If necessary, the profiles 21 and 22 are adapted to have at least one locking stage making it possible to hermetically seal the bag at a temperature above 80° C. or even 100° C., the corresponding locking stage being formed according to the embodiments described with reference to FIG. 2.

For example, several locking stages may be adapted to seal the bag, which makes the user more confident with regard to the hermeticity of the bag once it has been sealed than if the profiles only comprise one locking stage. According to another embodiment, the closing device 20 of the bag 1 may comprise two levels of profiles 21, 22, 23, 24, or more, each level comprising a male profile 21, 23, and a corresponding female profile 22, 24, and the pairs of profiles being positioned at different distances from the mouth of the bag. This example is illustrated in FIG. 4.

Moreover, one or more pairs of profiles may be adapted to seal the bag by the embodiment explained with reference to FIG. 2.

For example, with reference to FIG. 4, only the pair of profiles 31, 32, the closest to the mouth may be adapted to make it possible to seal the bag. Thus, once the bag is sealed, it can be re-opened later by cutting its walls between two levels of profiles, and the remaining profiles may be used to re-close and re-open the bag later.

All or part of the pairs of profiles may be provided with several locking levels according to the embodiment of which an example is illustrated in FIG. 3.

Finally, for a greater contact surface area between the engaging parts 212 and 222 of the profiles 21 and 22, these may be revolving cylinder sections, as illustrated in FIGS. 2 c and 2 d.

The bag 1 having the aforementioned characteristics may thus be used for the sterilisation and the preservation of food products. In fact, it withstands a temperature of 100° C., to which the products are heated to sterilise them, and thanks to this temperature its closing means hermetically seal the bag, thereby protecting it from any contamination or oxidation by the exterior atmosphere.

With reference to FIG. 3, a method of sterilisation of food products P, by use of a bag 1 according to the invention, will now be described.

In FIG. 3 a, food products P to be sterilised and preserved are inserted into a bag 1.

In FIG. 3 b, the bag 1 is closed by means of the closing device 20, preferably by engaging the parts 212 and 222 of the complementary closing profiles 21 and 22. Then the bag 1 filled with food products P is placed in an atmosphere A, the temperature of which is raised to 100° C. Typically, in traditional culinary applications, the atmosphere A is a water bath, in other words a recipient of water heated to boiling or in an autoclave at 115° C.

Finally, as in FIG. 3 c, thanks to the temperature of the atmosphere A, or to vapours therefrom or from food products P, the engaging parts 212 and 222 of profiles 21 and 22 are allowed to melt, partially or totally, in order that they hermetically seal the bag 1. Alternatively, the heat activatable adhesive on the engaging parts 212 and 222 is activated by the temperature of the atmosphere.

The bag 1 is moreover kept in the atmosphere A sufficiently long so that the sterilisation of the food products P takes place, typically between several tens of minutes and several hours for traditional food preserves.

Once this method has been completed, a hermetically closed bag 1 is obtained, containing sterilised food products P, which can be preserved as long as traditional preserves.

Obviously, the present invention is in no way limited to the embodiments described above and represented in the drawings, but those skilled in the art will know how to make numerous variants and modifications. 

1. Packaging bag (1), for the sterilisation of food, comprising walls (10,11) on which a closing device (20) is arranged, comprising complementary closing profiles (21, 22), said bag (1) being characterised in that: the constituent material of the wall has, at a temperature of 100° C., sufficient resistance to retain its confinement properties, and the complementary closing profiles (21, 22) are adapted to hermetically seal the bag (1) when it is placed in an atmosphere (A) of temperature above 80° C.
 2. Packaging bag according to claim 1, wherein the walls (10, 11) of the bag (1) are made of a material forming oxygen barrier.
 3. Packaging bag (1) according to claim 2, wherein the walls (10, 11) of the bag (1) are made of a material from the following group: polypropylene, polyethylene terephthalate-polypropylene complex, or polypropylene-polyamide complex.
 4. Packaging bag (1) according to claim 1, characterised in that the walls (10, 11) have a melting temperature above 120°.
 5. Packaging bag (1) according to claim 1, comprising several pairs of complementary closing profiles (21, 22, 23, 24), arranged at different distances from the mouth (E) of the bag (1).
 6. Packaging bag (1) according to claim 1, wherein at least one pair of complementary closing profiles (21, 22, 23, 24) has several locking levels.
 7. Packaging bag (1) according to claim 1, wherein at least one pair of complementary closing profiles (21, 22, 23, 24) is at least partially covered by an adhesive activatable from a temperature of 50° C., said bag (1) being hermetically sealed by melting of the adhesive when it is placed in an atmosphere (A) of temperature above 50° C.
 8. Packaging bag (1) according to the preceding claim, wherein at least one female profile (22) has an engaging part (222) in the form of a cavity, in which is arranged a strip of adhesive (C) activatable from a temperature of 50° C.
 9. Packaging bag (1) according to claim 1, wherein at least one pair of complementary closing profiles (21, 22) has engaging parts (212, 222) having a melting temperature comprised between 60° C. and 80° C., said bag (1) being hermetically sealed by melting of the engaging parts (212, 222) when it is placed in an atmosphere (A) of temperature above or equal to the melting temperature of the engaging parts (212, 222).
 10. Packaging bag (1) according to the preceding claim, wherein said engaging parts (212, 222) are composed of a polymer of ethylene vinyl acetate or ethylene ethyl acrylate, coextruded on the walls (10, 11) of the bag (1).
 11. Packaging bag (1) according to claim 1, wherein the complementary closing profiles (21, 22) are profiles of revolving cylinder section.
 12. Packaging bag (1) according to claim 1, wherein the closing device (20) is positioned near to the mouth (E) of the bag (1) formed by the upper edges (12) of the walls (10, 11), but set back with respect to said upper edges (12) of the walls (10, 11) of the bag (1).
 13. Use of a packaging bag (1) according to one of the preceding claims for the sterilisation and the preservation of food products (P).
 14. Method of sterilising food products (P), comprising the steps consisting in: inserting, into a bag (1) according to one of claims 1 to 12, a quantity of food products (P) to be sterilised, closing the bag (1) by means of the closing device (20), heating the bag (1), filled and closed in an atmosphere (A), to a temperature above or equal to 100° C., maintaining the bag (1) at temperature until the closing device (20) hermetically seals the bag (1) and until the food products (P) are sterilised. 